U.S. patent number 6,178,947 [Application Number 09/384,438] was granted by the patent office on 2001-01-30 for control apparatus for internal combustion engine with electronically-controlled throttle system.
This patent grant is currently assigned to Nissan Motor Co., Ltd., Unisia Jecs Corporation. Invention is credited to Hideki Hyoudou, Masahiro Iriyama, Kenichi Machida, Masaru Mizuguchi, Mikio Nozaki.
United States Patent |
6,178,947 |
Machida , et al. |
January 30, 2001 |
Control apparatus for internal combustion engine with
electronically-controlled throttle system
Abstract
In a computer-controlled internal combustion engine with an
electronically-controlled throttle system, a duplex
throttle-position sensor system, a duplex accelerator-position
sensor system, and other engine/vehicle sensors/switches, a
sensor-failure detection and fail-safe system is configured to be
electronically connected to the two throttle position sensors, the
two accelerator position sensors and a vehicle-deceleration sensor
for responding to a failure in at least one of the two throttle
position sensors and the two accelerator position sensors for
failsafe purposes. The sensor-failure detection and fail-safe
system comprises a duplex failsafe system for the throttle-position
sensor system and a duplex failsafe system for the
accelerator-position sensor system, to provide superior fail-safe
functions despite the presence of a throttle-position sensor
failure and/or an accelerator-position sensor failure.
Inventors: |
Machida; Kenichi (Gunma,
JP), Iriyama; Masahiro (Yokohama, JP),
Hyoudou; Hideki (Yokohama, JP), Mizuguchi; Masaru
(Kanagawa, JP), Nozaki; Mikio (Kangawa,
JP) |
Assignee: |
Unisia Jecs Corporation
(Atsugi, JP)
Nissan Motor Co., Ltd. (Yokohama, JP)
|
Family
ID: |
17113977 |
Appl.
No.: |
09/384,438 |
Filed: |
August 27, 1999 |
Foreign Application Priority Data
|
|
|
|
|
Aug 28, 1998 [JP] |
|
|
10-244114 |
|
Current U.S.
Class: |
123/396; 123/397;
123/399 |
Current CPC
Class: |
F02D
11/106 (20130101); F02D 11/107 (20130101); F02D
2200/0404 (20130101); F02D 2200/602 (20130101); F02D
2400/08 (20130101) |
Current International
Class: |
F02D
11/10 (20060101); F02D 011/10 () |
Field of
Search: |
;123/396,397,398,399 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Solis; Erick
Attorney, Agent or Firm: Foley & Lardner
Claims
What is claimed is:
1. A control apparatus for an internal combustion engine with an
electronically-controlled throttle system having a throttle valve
disposed in an induction system and an actuator operating the
throttle valve so that an opening of the throttle valve is adjusted
to a desired opening, comprising:
a duplex throttle-position sensor system having two throttle
position sensors each detecting the opening of the throttle
valve;
a vehicle-deceleration sensor detecting a decelerating condition of
the engine and generating a deceleration indicative signal; and
a fail-safe system configured to be electronically connected to the
two throttle position sensors and the vehicle-deceleration sensor
for responding to a failure in at least one of the two throttle
position sensors for failsafe purposes; said fail-safe system
comprising
(1) a first failsafe section which controls the opening of the
throttle valve by a sensor signal value from an unfailed throttle
position sensor of the two throttle position sensors at a single
throttle-position sensor failure mode where one of the two throttle
position sensors is failed, to initiate a first failsafe mode,
(2) a second failsafe section which inhibits the first failsafe
mode in response to the deceleration indicative signal from said
vehicle-deceleration sensor during the first failsafe mode and
holds the throttle valve at a predetermined default opening, to
initiate a second failsafe mode, and
(3) a third failsafe section which detects if the sensor signal
value from the unfailed throttle position sensor is within a
predetermined sensor-abnormality diagnostic criterion range during
the second failsafe mode, and unconditionally continues to hold the
opening of the throttle valve at the predetermined default opening
when the sensor signal value from the unfailed throttle position
sensor is out of the predetermined sensor-abnormality diagnostic
criterion range.
2. The control apparatus as claimed in claim 1, wherein the
predetermined sensor-abnormality diagnostic criterion range is
defined in such a way that an upper limit of the predetermined
sensor-abnormality diagnostic criterion range is obtained by adding
a predetermined margin to the predetermined default opening and a
lower limit of the predetermined sensor-abnormality diagnostic
criterion range is obtained by subtracting the predetermined margin
from the predetermined default opening.
3. The control apparatus as claimed in claim 1, wherein said
vehicle-deceleration sensor comprises an idle switch which detects
an idling condition of the engine.
4. The control apparatus as claimed in claim 1, wherein said
vehicle-deceleration sensor comprises a brake switch which detects
if brakes are applied or released.
5. The control apparatus as claimed in claim 1, wherein the
electronically-controlled throttle system comprises a throttle
operating lever whose ends are connected respectively to a throttle
shaft of the throttle valve and the actuator, and a return spring
and a default spring connected to respective sides of the throttle
operating lever so that a biasing force of the return spring is
opposite to a biasing force of the default spring, and wherein the
predetermined default opening is set as a neutral position of the
throttle operating lever that the biasing force of the return
spring and the biasing force of the default spring are balanced to
each other under a condition where the actuator is
de-energized.
6. A control apparatus for an internal combustion engine with an
electronically-controlled throttle system having a throttle valve
disposed in an induction system and an actuator operating the
throttle valve so that an opening of the throttle valve is adjusted
to a desired opening, comprising:
a duplex throttle-position sensor system having two throttle
position sensors each detecting the opening of the throttle
valve;
a duplex accelerator-position sensor system having two accelerator
position sensors each detecting an amount of depression of an
accelerator pedal;
a vehicle-deceleration sensor detecting a decelerating condition of
the engine and generating a deceleration indicative signal; and
a fail-safe system configured to be electronically connected to the
two throttle position sensors, the two accelerator position sensors
and the vehicle deceleration sensor for responding to a failure in
at least one of the two throttle position sensors and the two
accelerator position sensors for failsafe purposes; said fail-safe
system comprising
(1) a first failsafe section which feedback-controls the opening of
the throttle valve by a sensor signal value from an unfailed
throttle position sensor of the two throttle position sensors at a
single throttle-position sensor failure mode where one of the two
throttle position sensors is failed, to initiate a first failsafe
mode,
(2) a second failsafe section which inhibits the first failsafe
mode in response to the deceleration indicative signal from said
vehicle-deceleration sensor during the first failsafe mode and
holds the throttle valve at a predetermined default opening, to
initiate a second failsafe mode,
(3) a third failsafe section which detects if the sensor signal
value from the unfailed throttle position sensor is within a
predetermined sensor-abnormality diagnostic criterion range during
the second failsafe mode, and unconditionally continues to hold the
opening of the throttle valve at the predetermined default opening
when the sensor signal value from the unfailed throttle position
sensor is out of the predetermined sensor-abnormality diagnostic
criterion range,
(4) a fourth failsafe section which sets the desired opening of the
throttle valve based on a sensor signal value from an unfailed
accelerator position sensor of the two accelerator position sensors
at a single accelerator-position sensor failure mode where one of
the two accelerator position sensors is failed and
feedback-controls the opening of the throttle valve by the desired
opening based on the sensor signal value from the unfailed
accelerator position sensor, to initiate a fourth failsafe mode,
and
(5) a fifth failsafe section which detects if the sensor signal
value from the unfailed accelerator position sensor is above a
predetermined threshold value correlating with an idling condition
of the engine during the fourth failsafe mode and during idling,
and unconditionally continues to hold the opening of the throttle
valve at the predetermined default opening when the sensor signal
value from the unfailed accelerator position sensor is above the
predetermined threshold value.
7. The control apparatus as claimed in claim 6, wherein said second
failsafe section inhibits the fourth failsafe mode in response to
the deceleration indicative signal from said vehicle-deceleration
sensor during the fourth failsafe mode and holds the throttle valve
at the predetermined default opening.
8. In a computer-controlled internal combustion engine with an
electronically-controlled throttle system having a throttle valve
disposed in an induction system and an actuator operating the
throttle valve so that an opening of the throttle valve is adjusted
to a desired opening, a duplex throttle-position sensor system
having two throttle position sensors each detecting the opening of
the throttle valve, a vehicle-deceleration sensor detecting a
decelerating condition of the engine and generating a deceleration
indicative signal, and a sensor-failure detection and fail-safe
system configured to be electronically connected to the two
throttle position sensors and the vehicle-deceleration sensor for
responding to a failure in at least one of the two throttle
position sensors for failsafe purposes, comprising:
(1) a first failsafe means for feedback-controlling the opening of
the throttle valve by a sensor signal value from an unfailed
throttle position sensor of the two throttle position sensors at a
single throttle-position sensor failure mode where one of the two
throttle position sensors is failed, to initiate a first failsafe
mode,
(2) a second failsafe means for inhibiting the first failsafe mode
in response to the deceleration indicative signal from said
vehicle-deceleration sensor during the first failsafe mode and
holding the throttle valve at a predetermined default opening, to
initiate a second failsafe mode, and
(3) a third failsafe means having a window comparator for executing
a diagnosis on abnormality in the unfailed throttle position sensor
by comparing the sensor signal value from the unfailed throttle
position sensor with a predetermined sensor-abnormality diagnostic
criterion range during the second failsafe mode, and determining
that the unfailed throttle position sensor is operating abnormally
when the sensor signal value from the unfailed throttle position
sensor is out of the predetermined sensor-abnormality diagnostic
criterion range, and unconditionally continuing to hold the opening
of the throttle valve at the predetermined default opening when the
unfailed throttle position sensor is operating abnormally.
9. The sensor-failure detection and fail-safe system as claimed in
claim 8, wherein the predetermined sensor-abnormality diagnostic
criterion range is defined in such a way that an upper limit of the
predetermined sensor-abnormality diagnostic criterion range is
obtained by adding a predetermined margin to the predetermined
default opening and a lower limit of the predetermined
sensor-abnormality diagnostic criterion range is obtained by
subtracting the predetermined margin from the predetermined default
opening.
10. The sensor-failure detection and fail-safe system as claimed in
claim 8, wherein said vehicle-deceleration sensor comprises an idle
switch which detects an idling condition of the engine.
11. The sensor-failure detection and fail-safe system as claimed in
claim 8, wherein said vehicle-deceleration sensor comprises a brake
switch which detects if brakes are applied or released.
12. The sensor-failure detection and fail-safe system as claimed in
claim 8, wherein the electronically-controlled throttle system
comprises a throttle operating lever whose ends are connected
respectively to a throttle shaft of the throttle valve and the
actuator, and a return spring and a default spring connected to
respective sides of the throttle operating lever so that a biasing
force of the return spring is opposite to a biasing force of the
default spring, and wherein the predetermined default opening is
set as a neutral position of the throttle operating lever that the
biasing force of the return spring and the biasing force of the
default spring are balanced to each other under a condition where
the actuator is de-energized.
13. In a computer-controlled internal combustion engine with an
electronically-controlled throttle system having a throttle valve
disposed in an induction system and an actuator operating the
throttle valve so that an opening of the throttle valve is adjusted
to a desired opening, a duplex throttle-position sensor system
having two throttle position sensors each detecting the opening of
the throttle valve, a duplex accelerator-position sensor system
having two accelerator position sensors each detecting an amount of
depression of an accelerator pedal, a vehicle-deceleration sensor
detecting a decelerating condition of the engine and generating a
deceleration indicative signal, and a sensor-failure detection and
fail-safe system configured to be electronically connected to the
two throttle position sensors, the two accelerator position sensors
and the vehicle-deceleration sensor for responding to a failure
in-at least one of the two throttle position sensors and the two
accelerator position sensors for failsafe purposes, comprising:
(1) a first failsafe means for feedback-controlling the opening of
the throttle valve by a sensor signal value from an unfailed
throttle position sensor of the two throttle position sensors at a
single throttle-position sensor failure mode where one of the two
throttle position sensors is failed, to initiate a first failsafe
mode,
(2) a second failsafe means for inhibiting the first failsafe mode
in response to the deceleration indicative signal from said
vehicle-deceleration sensor during the first failsafe mode and
holding the throttle valve at a predetermined default opening, to
initiate a second failsafe mode,
(3) a third failsafe means having a window comparator for executing
a diagnosis on abnormality in the unfailed throttle position sensor
by comparing the sensor signal value from the unfailed throttle
position sensor with a predetermined sensor-abnormality diagnostic
criterion range during the second failsafe mode, and determining
that the unfailed throttle position sensor is operating abnormally
when the sensor signal value from the unfailed throttle position
sensor is out of the predetermined sensor-abnormality diagnostic
criterion range, and unconditionally continuing to hold the opening
of the throttle valve at the predetermined default opening when the
unfailed throttle position sensor is operating abnormally,
(4) a fourth failsafe means for setting the desired opening of the
throttle valve based on a sensor signal value from an unfailed
accelerator position sensor of the two accelerator position sensors
at a single accelerator-position sensor failure mode where one of
the two accelerator position sensors is failed and
feedback-controlling the opening of the throttle valve by the
desired opening based on the sensor signal value from the unfailed
accelerator position sensor, to initiate a fourth failsafe mode,
and
(5) a fifth failsafe means having a comparator for executing a
diagnosis on abnormality in the unfailed accelerator position
sensor by comparing the sensor signal value from the unfailed
accelerator position sensor with a predetermined threshold value
correlating with an idling condition of the engine during the
fourth failsafe mode and during idling, and determining that the
unfailed accelerator position sensor is operating abnormally when
the sensor signal value from the unfailed accelerator position
sensor is above the predetermined threshold value, and
unconditionally continuing to hold the opening of the throttle
valve at the predetermined default opening when the unfailed
accelerator position sensor is operating abnormally.
14. The sensor-failure detection and fail-safe system as claimed in
claim 13, wherein said second failsafe means inhibits the fourth
failsafe mode in response to the deceleration indicative signal
from said vehicle-deceleration sensor during the fourth failsafe
mode and holds the throttle valve at the predetermined default
opening.
15. A method for executing failsafe functions for a
computer-controlled internal combustion engine with an
electronically-controlled throttle system having a throttle valve
disposed in an induction system and an actuator operating the
throttle valve so that an opening of the throttle valve is adjusted
to a desired opening, a duplex throttle-position sensor system
having two throttle position sensors each detecting the opening of
the throttle valve, a vehicle-deceleration sensor detecting a
decelerating condition of the engine and generating a deceleration
indicative signal, and a sensor-failure detection and fail-safe
system configured to be electronically connected to the two
throttle position sensors and the vehicle-deceleration sensor for
responding to a failure in at least one of the two throttle
position sensors for failsafe purposes, the method comprising:
feedback-controlling the opening of the throttle valve by a sensor
signal value from an unfailed throttle position sensor of the two
throttle position sensors at a single throttle-position sensor
failure mode where one of the two throttle position sensors is
failed, to initiate a first failsafe mode;
inhibiting the first failsafe mode in response to the deceleration
indicative signal from said vehicle-deceleration sensor during the
first failsafe mode and holding the throttle valve at a
predetermined default opening, to initiate a second failsafe
mode;
executing a diagnosis on abnormality in the unfailed throttle
position sensor by comparing the sensor signal value from the
unfailed throttle position sensor with a predetermined
sensor-abnormality diagnostic criterion range during the second
failsafe mode;
determining that the unfailed throttle position sensor is operating
abnormally when the sensor signal value from the unfailed throttle
position sensor is out of the predetermined sensor-abnormality
diagnostic criterion range; and
unconditionally continuing to hold the opening of the throttle
valve at the predetermined default opening when the unfailed
throttle position sensor is operating abnormally.
16. The method as claimed in claim 15, wherein the predetermined
sensor-abnormality diagnostic criterion range is defined in such a
way that an upper limit of the predetermined sensor-abnormality
diagnostic criterion range is obtained by adding a predetermined
margin to the predetermined default opening and a lower limit of
the predetermined sensor-abnormality diagnostic criterion range is
obtained by subtracting the predetermined margin from the
predetermined default opening.
17. The method as claimed in claim 15, wherein said
vehicle-deceleration sensor comprises an idle switch which detects
an idling condition of the engine.
18. The method as claimed in claim 15, wherein said
vehicle-deceleration sensor comprises a brake switch which detects
if brakes are applied or released.
19. The method as claimed in claim 15, wherein the
electronically-controlled throttle system comprises a throttle
operating lever whose ends are connected respectively to a throttle
shaft of the throttle valve and the actuator, and a return spring
and a default spring connected to respective sides of the throttle
operating lever so that a biasing force of the return spring is
opposite to a biasing force of the default spring, and wherein the
predetermined default opening is set as a neutral position of the
throttle operating lever that the biasing force of the return
spring and the biasing force of the default spring are balanced to
each other under a condition where the actuator is
de-energized.
20. A method for executing failsafe functions for a
computer-controlled internal combustion engine with an
electronically-controlled throttle system having a throttle valve
disposed in an induction system and an actuator operating the
throttle valve so that an opening of the throttle valve is adjusted
to a desired opening, a duplex throttle-position sensor system
having two throttle position sensors each detecting the opening of
the throttle valve, a duplex accelerator-position sensor system
having two accelerator position sensors each detecting an amount of
depression of an accelerator pedal, a vehicle-deceleration sensor
detecting a decelerating condition of the engine and generating a
deceleration indicative signal, and a sensor-failure detection and
fail-safe system configured to be electronically connected to the
two throttle position sensors, the two accelerator position sensors
and the vehicle-deceleration sensor for responding to a failure in
at least one of the two throttle position sensors and the two
accelerator position sensors for failsafe purposes, the method
comprising:
feedback-controlling the opening of the throttle valve by a sensor
signal value from an unfailed throttle position sensor of the two
throttle position sensors at a single throttle-position sensor
failure mode where one of the two throttle position sensors is
failed, to initiate a first failsafe mode;
inhibiting the first failsafe mode in response to the deceleration
indicative signal from said vehicle-deceleration sensor during the
first failsafe mode and holding the throttle valve at a
predetermined default opening, to initiate a second failsafe
mode;
executing a diagnosis on abnormality in the unfailed throttle
position sensor by comparing the sensor signal value from the
unfailed throttle position sensor with a predetermined
sensor-abnormality diagnostic criterion range during the second
failsafe mode;
determining that the unfailed throttle position sensor is operating
abnormally when the sensor signal value from the unfailed throttle
position sensor is out of the predetermined sensor-abnormality
diagnostic criterion range;
unconditionally continuing to hold the opening of the throttle
valve at the predetermined default opening when the unfailed
throttle position sensor is operating abnormally;
setting the desired opening of the throttle valve based on a sensor
signal value from an unfailed accelerator position sensor of the
two accelerator position sensors at a single accelerator-position
sensor failure mode where one of the two accelerator position
sensors is failed;
feedback-controlling the opening of the throttle valve by the
desired opening based on the sensor signal value from the unfailed
accelerator position sensor, to initiate a fourth failsafe
mode;
executing a diagnosis on abnormality in the unfailed accelerator
position sensor by comparing the sensor signal value from the
unfailed accelerator position sensor with a predetermined threshold
value correlating with an idling condition of the engine during the
fourth failsafe mode and during idling;
determining that the unfailed accelerator position sensor is
operating abnormally when the sensor signal value from the unfailed
accelerator position sensor is above the predetermined threshold
value; and
unconditionally continuing to hold the opening of the throttle
valve at the predetermined default opening when the unfailed
accelerator position sensor is operating abnormally.
21. The method as claimed in claim 20, wherein the fourth failsafe
mode is inhibited responsively to the deceleration indicative
signal from said vehicle-deceleration sensor during the fourth
failsafe mode and then the throttle valve is held at the
predetermined default opening.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a computer-controlled internal
combustion engine equipped with an electronically-controlled
throttle system capable of electronically controlling the opening
of the throttle valve, and more specifically to techniques for
executing a fail-safe control routine in presence of a failure or
an abnormality in a throttle position sensor located on the
throttle body of an electronically-controlled throttle system
and/or in an accelerator position sensor monitoring the amount of
depression of an accelerator pedal.
There are two typical types of electronically-controlled throttle
systems, one being a so-called half-electronically-controlled
throttle system and a so-called full-electronically-controlled
throttle system. The former half-electronically-controlled throttle
system has a manually-wire-operated throttle valve as well as an
electronically-controlled throttle valve which is commanded by an
electronic engine control unit (ECU) or an electronic control
module (ECM).
Usually, the electronically-controlled throttle valve is operated
arbitrarily in response to an instruction of the ECU, based on
engine/vehicle operating conditions, such as the amount of
depression of an accelerator pedal or the like. In the presence of
a failure either elsewhere in the ECU or within the sensor systems
(such as, shorted/opened sensor input signals), the throttle
control system switches from the full-electronically-controlled
throttle system to the manually-wire-operated throttle system, so
that the opening of the throttle valve is manually adjusted
depending on the accelerator pedal travel. One such
half-electronically-controlled throttle system has been disclosed
in Japanese Patent Provisional Publication No. 7-180570.
Later models of full-electronically-controlled throttle systems
utilize input informational signal data from two accelerator
position sensors and two throttle position sensors. Generally, the
ECU uses or selects a lower one of the sensor signals from the two
accelerator position sensors byway of a so-called select-LOW
process.
With respect to the throttle-opening indicative data, the ECU uses
an input signal from a main throttle position sensor out of the two
throttle position sensors, or selects a higher one of the sensor
signals from the two throttle position sensors by way of a
so-called select-HIGH process. If the failure occurs in either one
of the two throttle position sensors of the duplex
throttle-position sensor system, the throttle control system
ordinarily de-activates the throttle actuator, so as to hold the
opening of the electronically-controlled throttle valve at a
predetermined "default" opening or a predetermined "fail-safe"
opening, thereby putting the engine into its limp-home mode (or
limp-in mode). The limp-home mode allows the engine/vehicle to be
run/driven but with greatly reduced performance, (for example, the
vehicle can limp in at a maximum speed of 40 Km/h). It is so
inconvenient.
SUMMARY OF THE INVENTION
In case of a detected defective throttle-position sensor, it is
rational and desirable to properly control the opening of an
electronically-controlled throttle valve, using the input
information signal from the other sensor (e.g., the other throttle
position sensor in a duplex throttle-position sensor system).
Furthermore, if the other throttle position sensor fails or
operates abnormally, it is desirable to substitute a default
opening (a fail-safe opening) for the second failed sensor.
Accordingly, it is an object of the invention to provide an
integrated engine control system which is capable of assuring a
high-quality, reliable internal combustion engine with an
electronically-controlled throttle system, by at least a duplex
fail-safe system despite the presence of throttle-position sensor
failures or faults.
It is another object of the invention to provide an integrated
engine control system which is capable of assuring a high-quality,
reliable internal combustion engine with an
electronically-controlled throttle system, by at least a duplex
fail-safe system despite the presence of accelerator-position
sensor failures or faults.
It is a still further object of the invention to provide an
integrated engine control system which is capable of assuring a
high-quality, reliable internal combustion engine with an
electronically-controlled throttle system, by at least a duplex
fail-safe system for a throttle-position sensor system despite the
presence of a throttle-position sensor failure or fault and by at
least a duplex fail-safe system for an accelerator-position sensor
system despite the presence of an accelerator-position sensor
failure or fault.
In order to accomplish the aforementioned and other objects of the
present invention, a control apparatus for an internal combustion
engine with an electronically-controlled throttle system having a
throttle valve disposed in an induction system and an actuator
operating the throttle valve so that an opening of the throttle
valve is adjusted to a desired opening, comprises a duplex
throttle-position sensor system having two throttle position
sensors each detecting the opening of the throttle valve, a
vehicle-deceleration sensor detecting a decelerating condition of
the engine and generating a deceleration indicative signal, and a
fail-safe system configured to be electronically connected to the
two throttle position sensors and the vehicle-deceleration sensor
for responding to a failure in at least one of the two throttle
position sensors for failsafe purposes, the fail-safe system
comprising a first failsafe section which controls the opening of
the throttle valve by a sensor signal value from an unfailed
throttle position sensor of the two throttle position sensors at a
single throttle-position sensor failure mode where one of the two
throttle position sensors is failed, to initiate a first failsafe
mode, a second failsafe section which inhibits the first failsafe
mode in response to the deceleration indicative signal from the
vehicle-deceleration sensor during the first failsafe mode and
holds the throttle valve at a predetermined default opening, to
initiate a second failsafe mode, and a third failsafe section which
detects if the sensor signal value from the unfailed throttle
position sensor is within a predetermined sensor-abnormality
diagnostic criterion range during the second failsafe mode, and
unconditionally continues to hold the opening of the throttle valve
at the predetermined default opening when the sensor signal value
from the unfailed throttle position sensor is out of the
predetermined sensor-abnormality diagnostic criterion range.
According to another aspect of the invention, a control apparatus
for an internal combustion engine with an electronically-controlled
throttle system having a throttle valve disposed in an induction
system and an actuator operating the throttle valve so that an
opening of the throttle valve is adjusted to a desired opening,
comprises a duplex throttle-position sensor system having two
throttle position sensors each detecting the opening of the
throttle valve, a duplex accelerator-position sensor system having
two accelerator position sensors each detecting an amount of
depression of an accelerator pedal, a vehicle-deceleration sensor
detecting a decelerating condition of the engine and generating a
deceleration indicative signal, and a fail-safe system configured
to be electronically connected to the two throttle position
sensors, the two accelerator position sensors and the
vehicled-deceleration sensor for responding to a failure in at
least one of the two throttle position sensors and the two
accelerator position sensors for failsafe purposes, the fail-safe
system comprising a first failsafe section which feedback-controls
the opening of the throttle valve by a sensor signal value from an
unfailed throttle position sensor of the two throttle position
sensors at a single throttle-position sensor failure mode where one
of the two throttle position sensors is failed, to initiate a first
failsafe mode, a second failsafe section which inhibits the first
failsafe mode in response to the deceleration indicative signal
from the vehicle-deceleration sensor during the first failsafe mode
and holds the throttle valve at a predetermined default opening, to
initiate a second failsafe mode, a third failsafe section which
detects if the sensor signal value from the unfailed throttle
position sensor is within a predetermined sensor-abnormality
diagnostic criterion range during the second failsafe mode, and
unconditionally continues to hold the opening of the throttle valve
at the predetermined default opening when the sensor signal value
from the unfailed throttle position sensor is out of the
predetermined sensor-abnormality diagnostic criterion range, a
fourth failsafe section which sets the desired opening of the
throttle valve based on a sensor signal value from an unfailed
accelerator position sensor of the two accelerator position sensors
at a single accelerator-position sensor failure mode where one of
the two accelerator position. sensors is failed and
feedback-controls the opening of the throttle valve by the desired
opening based on the sensor signal value from the unfailed
accelerator position sensor, to initiate a fourth failsafe mode,
and a fifth failsafe section which detects if the sensor signal
value from the unfailed accelerator position sensor is above a
predetermined threshold value correlating with an idling condition
of the engine during the fourth failsafe mode and during idling,
and unconditionally continues to hold the opening of the throttle
valve at the predetermined default opening when the sensor signal
value from the unfailed accelerator position sensor is above the
predetermined threshold value. Preferably, the second failsafe
section inhibits the fourth failsafe mode in response to the
deceleration indicative signal during the fourth failsafe mode and
holds the throttle valve at the predetermined default opening.
According to a further aspect of the invention, in
computer-controlled internal combustion engine with an
electronically-controlled throttle system having a throttle valve
disposed in an induction system and an actuator operating the
throttle valve so that an opening of the throttle valve is adjusted
to a desired opening, a duplex throttle-position sensor system
having two throttle position sensors each detecting the opening of
the throttle valve, a vehicle-deceleration sensor detecting a
decelerating condition of the engine and generating a deceleration
indicative signal, and a sensor-failure detection and fail-safe
system configured to be electronically connected to the two
throttle position sensors and the vehicle-deceleration sensor for
responding to a failure in at least one of the two throttle
position sensors for failsafe purposes, comprises a first failsafe
means for feed back controlling the opening of the throttle valve
by a sensor signal value from an unfailed throttle position sensor
of the two throttle position sensors at a single throttle-position
sensor failure mode where one of the two throttle position sensors
is failed, to initiate a first failsafe mode, a second failsafe
means for inhibiting the first failsafe mode in response to the
deceleration indicative signal from the vehicle-deceleration sensor
during the first failsafe mode and holding the throttle valve at a
predetermined default opening, to initiate a second failsafe mode,
and a third failsafe means having a window comparator for executing
a diagnosis on abnormality in the unfailed throttle position sensor
by comparing the sensor signal value from the unfailed throttle
position sensor with a predetermined sensor-abnormality diagnostic
criterion range during the second failsafe mode, and determining
that the unfailed throttle position sensor is operating abnormally
when the sensor signal value from the unfailed throttle position
sensor is out of the predetermined sensor-abnormality diagnostic
criterion range, and unconditionally continuing to hold the opening
of the throttle valve at the predetermined default opening when the
unfailed throttle position sensor is operating abnormally.
According to a still further aspect of the invention, in a
computer-controlled internal combustion engine with an
electronically-controlled throttle system having a ,throttle valve
disposed in an induction system and an actuator operating the
throttle valve so that an opening of the throttle valve is adjusted
to a desired opening, a duplex throttle-position sensor system
having two throttle position sensors each detecting the opening of
the throttle valve, a duplex accelerator-position sensor system
having two accelerator position sensors each detecting an amount of
depression of an accelerator pedal, a vehicle-deceleration sensor
detecting a decelerating condition of the engine and generating a
deceleration indicative signal, and a sensor-failure detection and
fail-safe system configured to be electronically connected to the
two throttle position sensors, the two accelerator position sensors
and the vehicle-deceleration sensor for responding to a failure in
at least one of the two throttle position sensors and the two
accelerator position sensors for failsafe purposes, comprises a
first failsafe means for feedback-controlling the opening of the
throttle valve by a sensor signal value from an unfailed throttle
position sensor of the two throttle position sensors at a single
throttle-position sensor failure mode where one of the two throttle
position sensors is failed, to initiate a first failsafe mode, a
second failsafe means for inhibiting the first failsafe mode in
response to the deceleration indicative signal from the
vehicle-deceleration sensor during the first failsafe mode and
holding the throttle valve at a predetermined default opening, to
initiate a second failsafe mode, a third failsafe means having a
window comparator for executing a diagnosis on abnormality in the
unfailed throttle position sensor by comparing the sensor signal
value from the unfailed throttle position sensor with a
predetermined sensor-abnormality diagnostic criterion range during
the second failsafe mode, and determining that the unfailed
throttle position sensor is operating abnormally when the sensor
signal value from the unfailed throttle position sensor is out of
the predetermined sensor-abnormality diagnostic criterion range,
and unconditionally continuing to hold the opening of the throttle
valve at the predetermined default opening when the unfailed
throttle position sensor is operating abnormally, a fourth failsafe
means for setting the desired opening of the throttle valve based
on a sensor signal value from an unfailed accelerator position
sensor of the two accelerator position sensors at a single
accelerator-position sensor failure mode where one of the two
accelerator position sensors is failed and feedback-controlling the
opening of the throttle valve by the desired opening based on the
sensor signal value from the unfailed accelerator position sensor,
to initiate a fourth failsafe mode, and a fifth failsafe means
having a comparator for executing a diagnosis on abnormality in the
unfailed accelerator position sensor by comparing the sensor signal
value from the unfailed accelerator position sensor with a
predetermined threshold value correlating with an idling condition
of the engine during the fourth failsafe mode and during idling,
and determining that the unfailed accelerator position sensor is
operating abnormally when the sensor signal value from the unfailed
accelerator position sensor is above the predetermined threshold
value, and unconditionally continuing to hold the opening of the
throttle valve at the predetermined default opening when the
unfailed accelerator position sensor is operating abnormally.
According to another aspect of the invention, a method for
executing failsafe functions for a computer-controlled internal
combustion engine with an electronically-controlled throttle system
having a throttle valve disposed in an induction system and an
actuator operating the throttle valve so that an opening of the
throttle valve is adjusted to a desired opening, a duplex
throttle-position sensor system having two throttle position
sensors each detecting the opening of the throttle valve, a
vehicle-deceleration sensor detecting a decelerating condition of
the engine and generating a deceleration indicative signal, and a
sensor-failure detection and fail-safe system configured to be
electronically connected to the two throttle position sensors and
the vehicle-deceleration sensor for responding to a failure in at
least one of the two throttle position sensors for failsafe
purposes, the method comprises feedback-controlling the opening of
the throttle valve by a sensor signal value from an unfailed
throttle position sensor of the two throttle position sensors at a
single throttle-position sensor failure mode where one of the two
throttle position sensors is failed, to initiate a first failsafe
mode, inhibiting the first failsafe mode in response to the
deceleration indicative signal from the vehicle-deceleration sensor
during the first failsafe mode and holding the throttle valve at a
predetermined default opening, to initiate a second failsafe mode,
executing a diagnosis on abnormality in the unfailed throttle
position sensor by comparing the sensor signal value from the
unfailed throttle position sensor with a predetermined
sensor-abnormality diagnostic criterion range during the second
failsafe mode, determining that the unfailed throttle position
sensor is operating abnormally when the sensor signal value from
the unfailed throttle position sensor is out of the predetermined
sensor-abnormality diagnostic criterion range, and unconditionally
continuing to hold the opening of the throttle valve at the
predetermined default opening when the unfailed throttle position
sensor is operating abnormally.
According to another aspect of the invention, a method for
executing failsafe functions for a computer-controlled internal
combustion engine with an electronically-controlled throttle system
having a throttle valve disposed in an induction system and an
actuator operating the throttle valve so that an opening of the
throttle valve is adjusted to a desired opening, a duplex
throttle-position sensor system having two throttle position
sensors each detecting the opening of the throttle valve, a duplex
accelerator-position sensor system having two accelerator position
sensors each detecting an amount of depression of an accelerator
pedal, a vehicle-deceleration sensor detecting a decelerating
condition of the engine and generating a deceleration indicative
signal, and a sensor-failure detection and fail-safe system
configured to be electronically connected to the two throttle
position sensors, the two accelerator position sensors and the
vehicle-deceleration sensor for responding to a failure in at least
one of the two throttle position sensors and the two accelerator
position sensors for failsafe purposes, the method comprises
feedback-controlling the opening of the throttle valve by a sensor
signal value from an unfailed throttle position sensor of the two
throttle position sensors at a single sensor failure mode where one
of the two throttle position sensors is failed, to initiate a first
failsafe mode, inhibiting the first failsafe mode in response to
the deceleration indicative signal from the vehicle-deceleration
sensor during the first failsafe mode and holding the throttle
valve at a predetermined default opening, to initiate a second
failsafe mode, executing a diagnosis on abnormality in the unfailed
throttle position sensor by comparing the sensor signal value from
the unfailed throttle position sensor with a predetermined
sensor-abnormality diagnostic criterion range during the second
failsafe mode, determining that the unfailed throttle position
sensor is operating abnormally when the sensor signal value from
the unfailed throttle position sensor is out of the predetermined
sensor-abnormality diagnostic criterion range, unconditionally
continuing to hold the opening of the throttle valve at the
predetermined default opening when the unfailed throttle position
sensor is operating abnormally, setting the desired opening of the
throttle valve based on a sensor signal value from an unfailed
accelerator position sensor of the two accelerator position sensors
at a single accelerator-position sensor failure mode where one of
the two accelerator position sensors is failed,
feedback-controlling the opening of the throttle valve by the
desired opening based on the sensor signal value from the unfailed
accelerator position sensor, to initiate a fourth failsafe mode,
executing a diagnosis on abnormality in the unfailed accelerator
position sensor by comparing the sensor signal value from the
unfailed accelerator position sensor with a predetermined threshold
value correlating with an idling condition of the engine during the
fourth failsafe mode and during idling, determining that the
unfailed accelerator position sensor is operating abnormally when
the sensor signal value from the unfailed accelerator position
sensor is above the predetermined threshold value, and
unconditionally continuing to hold the opening of the throttle
valve at the predetermined default opening when the unfailed
accelerator position sensor is operating abnormally.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a system diagram illustrating one embodiment of a
computer-controlled internal combustion engine with an
electronically-controlled throttle system.
FIG. 2 is a logic circuit arrangement showing the relationship
among diagnosis results of accelerator position sensors, diagnosis
results of throttle position sensors, a switched-ON operation of a
warning lamp, a turned-OFF operation of a power transistor, and a
switched-OFF operation of a relay.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, particularly to FIG. 1, the control
apparatus of the invention is exemplified in an in-cylinder
direct-injection spark-ignition internal combustion engine 4
equipped with an electronically-controlled throttle valve 9, a
duplex throttle-position sensor system (or a duplex TPS sensor
system 14A, 14B), and a duplex accelerator-position sensor system
(a duplex APS sensor system 1A, 1B). As seen in FIG. 1, reference
signs 1A and 1B denote two accelerator position sensors (two APS
sensors) included in the duplex accelerator-position sensor system,
each provided for detecting the amount of depression of the
accelerator pedal. Although it is not clearly shown in FIG. 1, an
accelerator wire (not shown) is connected between the accelerator
pedal and an accelerator drum (not shown), and each of the
accelerator position sensors 1A and 1B is connected to the
accelerator drum on which part of the accelerator wire is wound.
Thus, in the duplex accelerator-position sensor system, as the
accelerator angle (the amount of depression of the accelerator
pedal) is increased, the sensor signal (e. g. a voltage signal)
from each of the accelerator-position sensors 1A and 1B increases.
Reference sign 2 denotes a crank angle sensor. The crank angle
sensor 2 is provided for detecting revolutions of the engine
crankshaft or rotation of the camshaft. Assuming that the number of
engine cylinders is "n", the crank angle sensor 2 generates a
reference pulse signal REF at a predetermined crank angle for every
crank angle 720.degree./n, and at the same time generates a unit
pulse signal POS (1.degree.) for every unit crank angle
(1.degree.). The central processing unit (CPU) of the ECU 19
arithmetically calculates or estimates engine speed on the basis of
the period of the reference pulse signals REF and the unit pulse
signals POS, while counting the number of generation of the POS
signals per a unit time and/or monitoring the period between
generations of the two adjacent reference signals. An air flow
meter 3 is provided in the induction system downstream of an air
cleaner (not shown) for detecting or measuring the actual volume of
air flowing into the engine cylinders. The quantity of intake air
supplied per a unit time is defined as an intake-airflow rate. An
engine temperature sensor is located on the engine and usually
screwed into one of the top coolant passages to detect or sense an
actual operating temperature of the engine, (an engine temperature
such as an engine coolant temperature). The electronic fuel
injection system of the direct-injection spark-ignition engine
includes an electromagnetic fuel-injection valve (simply an
electromagnetic fuel injector) 6 provided at each engine cylinder,
so that fuel (gasoline) can be injected or sprayed directly into
each combustion chamber. The electronic ignition system of the
direct-injection spark-ignition engine includes a spark plug 7
screwed into the cylinder head to ignite the air-fuel mixture. The
direct-injection spark ignition engine uses at least two combustion
modes, one being an early injection combustion mode (or a
homogeneous combustion mode) where fuel-injection early in the
intake stroke produces a homogeneous air-fuel mixture, and the
other being a late injection combustion mode (or a stratified
combustion mode) where late fuel-injection delays the event until
near the end of the compression stroke to produce a stratified
air-fuel mixture. During the homogeneous combustion mode, the early
injection in the intake stroke enables the fuel spray to be
diffused within the combustion chamber and then to be mixed more
uniformly with the air. During the stratified combustion mode, the
incoming air mixes with the denser fuel spray due to the late
injection in the compression stroke, to create a rich mixture
around the spark plug 7 for easy ignition, while the rest of the
air-fuel mixture after late injection is very lean at edges of the
combustion chamber. The electronic ignition system of the
direct-injection spark-ignition engine 4 is responsive to an
ignition signal from an electronic engine control unit (ECU or C/U)
19 or an electronic engine control module (ECM), for timely
igniting the air-fuel mixture to ensure the homogeneous combustion
on the intake stroke and to ensure the stratified combustion on the
compression stroke. All air, entering the combustion chamber of
each engine A cylinder of the engine 4, passes first through the
air cleaner (not shown) and the air flow meter 3, flow via an
intake-air passage 8 toward the electronically-controlled throttle
valve 9. The electronically controlled throttle valve 9 is disposed
in the intake-air passage 8 of the induction system, to
electronically control the throttle opening (i.e., the flow rate of
intake air entering each intake-valve port), arbitrarily depending
on the engine/vehicle operating conditions (e.g., the amount of
depression of an accelerator pedal or the like). For the
throttle-opening adjustment, the electronically-controlled throttle
valve 9 is actuated or operated by a throttle actuator 11 by virtue
of a throttle operating lever 10. One end of the throttle operating
lever 10 is fixedly connected to the throttle valve shaft of the
throttle valve 9, whereas the other end of the throttle operating
lever 10 is connected to the throttle actuator 11. As seen in FIG.
1, a return spring 12 and a default spring 13 are provided so that
the spring bias of the return spring 12 is opposite to the spring
bias of the default spring 13. The return spring 12 and the default
spring 13 are connected respectively to left-hand and right-hand
sides of the throttle operating lever 10, in such a way that the
throttle valve 9 is held at its "default" opening (or "default"
position) corresponding to a neutral position of the throttle
operating lever 10 that spring biases caused by the return spring
12 and the default spring 13 are balanced to each other, when the
throttle actuator 11 is de-energized. The electronically-controlled
throttle valve 9, the throttle operating lever 10, the throttle
actuator 11, the return spring 12, and the default spring 13
construct an electronically-controlled throttle system. Two
throttle position sensors (two TPS sensors) 14A and 14B included in
the duplex throttle-position sensor system are connected to the
throttle valve shaft of the electronically-controlled throttle
valve 9, for detecting an actual opening of the throttle valve 9.
Usually, each of the throttle position sensors 14A and 14b is
comprised of a variable resistor (a potentiometer) connected to the
throttle valve shaft of the throttle valve 9, so that when the
opening of the throttle valve 9 varies, a variable resistance
voltage signal is sensed at the ECU 19. An air/fuel ratio (A/F
ratio) sensor 16, such as 02 sensor, is located in an exhaust-gas
passage 15 of the exhaust system (in either the engine exhaust
manifold or piping) for monitoring the percentage of oxygen
contained within engine exhaust gases at all times when the engine
is running, so that the ECU 19 can maintain the A/F ratio at as
close to stoichiometric as possible for complete fuel combustion
and minimum exhaust emissions. Reference sign 17 denotes an idle
switch (or an idle position switch) that is generally installed on
the throttle body. The idle switch 17 is only energized when the
throttle is at its closed position (or idle position). The position
of the idle switch 17 provides a voltage signal to the ECU 19 so as
to control fuel delivery pulse time of each of the fuel injectors 6
especially during deceleration or during idle speed. Reference sign
18 denotes a brake switch located near the brake pedal for
detecting whether the brakes are applied or released. Each of the
idle switch 17 and the brake switch 18 functions to detect a
decelerating condition of the engine/vehicle. The input interface
of the ECU 19 receives various sensor/switch signals from the
accelerator position sensors 1A and 1B, the crank angle sensor 2,
the air flow meter 3, the engine temperature sensor 5, the throttle
position sensors 14A and 14B, the A/F ratio sensor 16 (O.sub.2
sensor), the idle switch 17, and the brake switch 18. The ECU 19
determines a control signal value or a drive signal value for the
throttle actuator 11 depending on the operating conditions
estimated from the input informational signal data from these
engine/vehicle sensors/switches, so as to output the determined
control signal via its output interface to the throttle actuator 11
and to properly control the opening of the throttle valve 9. The
output interface of the ECU 19 also generates a drive signal to
each of the fuel injectors 6 to properly control the fuel injection
amount (or the fuel delivery pulse time) as required. At the same
time, the CPU of the ECU 19 arithmetically calculates or computes a
desired ignition timing based on the input information from the
previously-noted sensors/switches to perform a spark-timing control
suitable to the operating conditions monitored.
Referring now to FIG. 2, there is shown a sensor failure diagnosis
plus fail-safe control routine executed by a failure-detection and
failsafe system and based on the diagnosis results of the
accelerator position sensors (1A, 1B) and the diagnosis results of
the throttle position sensors (14A, 14B).
In FIG. 2, the left-hand half of the logic circuit arrangement
corresponds to the accelerator-position sensor system failure
diagnostic circuit, whereas the right-hand half of the logic
circuit arrangement corresponds to the throttle-position sensor
system failure diagnostic circuit. In the left-hand sensor failure
diagnosis/detection circuit related to the accelerator-position
sensor system, as seen from the leftmost block (APS1 sensor
signal-value diagnosis block), a sensor failure detection is, first
of all, made to determine whether an opened/shorted
accelerator-position sensor circuit exists, on the basis of a
shorted/opened input signal from the first accelerator position
sensor 1A. When the first accelerator position sensor 1A (or APS1)
is failed or when the shorted/opened signal from the first
accelerator position sensor 1A (or APS1) occurs, a first
accelerator-position sensor failure indicative flag APS1CA is set
at "1". To eliminate a transient sensor failure, a further check is
made to determine whether the sensor failure in the first
accelerator position sensor 1A is continually detected for a
predetermined delay time. In case that the failed-sensor state of
the first accelerator position sensor 1A continues for the
predetermined delay time, a first acceleration-position sensor
failure decision flag APS1NG is set at "1". In the same manner, as
seen from the center block (APS2 sensor signal-value diagnosis
block), a sensor failure detection is made to check whether an
opened/shorted accelerator-position sensor circuit exists, on the
basis of a shorted/opened input signal from the second accelerator
position sensor 1B. When the second accelerator position sensor 1B
(or APS2) is failed or when the shorted/opened signal from the
second accelerator position sensor 1B (or APS2) occurs, a second
accelerator-position sensor failure indicative flag APS2CA is set
at "1". When the failed-sensor state of the second accelerator
position sensor 1B continues for the predetermined delay time, a
second acceleration-position sensor failure decision flag APS2NG is
set at "1". In this manner, the first accelerator-position sensor
failure and the second accelerator-position sensor failure are
detected and decided. In the sensor failure diagnosis plus
fail-safe control sequence, the setting of each of the flags
APS1CA, APS1NG, APS2CA, APS2NG, APSXCA, APSXNG, TPS1CA, TPS1NG,
TPS2CA, TPS2NG, TPSXCA, TPSXNG, PWR.-TRANSISTOR OFF FLAG, RELAY OFF
FLAG, and LIMP-HOME ENABLING FLAG means the output of a high-level
voltage signal to each of circuits which will be fully described
later, whereas the resetting of each of the same flags means the
output of a low-level voltage signal to each of the circuits
(described later). Additionally, as seen from the rightmost block
(APS signal-mismatching diagnosis block), an APS signal-mismatching
diagnosis is made to determine if there is the mismatching between
values of two sensor signals from the two accelerator position
sensors 1A and 1B of the duplex accelerator-position sensor system.
In case that there is the signal mismatching between the values of
sensor signals from the two accelerator position sensors 1A (or
APS1) and 1B (or APS2), a signal-mismatching indicative flag APSXCA
is set at "1". To eliminate a transient APS signal mismatching
state, a further check is made to determine whether the signal
mismatching state between the two accelerator position sensors (1A,
1B) continues for a predetermined delay time. In case that the
signal mismatching state for the duplex APS sensor system continues
for the predetermined delay time, an APS signal-mismatching state
decision flag APSXNG is set at "1" in order to decide such a
signal-mismatching state in the duplex accelerator-position sensor
system.
Similarly to the above, in the right-hand sensor failure
diagnosis/detection circuit related to the throttle-position sensor
system, as seen from the leftmost block (TPS1 sensor signal-value
diagnosis block) and the center block (TPS2 sensor signal-value
diagnosis block), a check is made to determine whether an
opened/shorted throttle-position sensor circuit exists, on the
basis of shorted/opened input signals from the first and second
throttle position sensor 14A and 14B. When the first throttle
position sensor 14A (or TPS1) is failed or when the shorted/opened
signal from the first throttle position sensor 14A (or TPS1)
occurs, a first throttle-position sensor failure indicative flag
TPS1CA is set at "1". A further check is made to determine whether
the sensor failure in the first throttle position sensor 14A is
continually detected for a predetermined delay time. In case that
the failed-sensor state of the first throttle position sensor 14A
continues for the predetermined delay time, a first
throttle-position sensor failure decision flag TPS1NG is set at
"1". In the same manner, a sensor failure detection is made to
check whether an opened/shorted throttle-position sensor circuit
exists, on the basis of a shorted/opened input signal from the
second throttle position sensor 14B. When the second throttle
position sensor 14B (or TPS2) is failed or when the shorted/opened
signal from the second throttle position sensor 14B (or TPS2)
occurs, a second throttle-position sensor failure indicative flag
TPS2CA is set at "1". When the failed-sensor state of the second
throttle position sensor 14B continues for the predetermined delay
time, a second throttle-position sensor failure decision flag
TPS2NG is set at "1". In this manner, the first throttle-position
sensor failure and the second throttle-position sensor failure are
detected and decided. In addition, as seen from the rightmost block
(TPS signal-mismatching diagnosis block), a TPS signal-mismatching
diagnosis is made to determine if there is the mismatching between
values of two sensor signals from the two throttle position sensors
14A and 14B of the duplex throttle-position sensor system. In case
that there is the signal mismatching between the values of sensor
signals from the two throttle position sensors 14A (or TPS1) and
14B (or TPS2), a TPS signal-mismatching indicative flag TPSXCA is
set at "1". To eliminate a transient TPS signal mismatching state,
a further check is made to determine whether the signal mismatching
state between the two throttle position sensors (14A, 14B)
continues for a predetermined delay time. In case that the signal
mismatching state for the duplex TPS sensor system continues for
the predetermined delay time, a signal-mismatching state decision
flag TPSXNG is set at "1" in order to decide such a
signal-mismatching state in the duplex throttle-position sensor
system.
In case that the first and second acceleration-position sensor
failure decision flags APS1NG and APS2NG, and the APS
signal-mismatching indicative flag APSXCA are all reset to "0" (see
the first line from the top on the right-hand side APS sensor
system diagnosis table of FIG. 2), that is, when all of the
accelerator-position sensor circuits of the APS sensor system are
operating normally, the ECU 19 selects a lower one of the sensor
signal values from the two accelerator position sensors 1A and 1B
by way of a so-called select-LOW process. The select-LOW process
for selection of an accelerator-pedal opening (APO) is effective to
prevent excessive engine power output. In other words., a selection
value (an APO selection value) of the accelerator-pedal opening
(APO) is set at a lower one (LOWER) of the two APS sensor signal
values. On the other hand, in case that the first and second
throttle-position sensor failure decision f-lags TPS1NG and TPS2NG,
and the TPS signal-mismatching indicative flag TPSXCA are all reset
to "0" (see the first line from the top on the right-hand side TPS
sensor system diagnosis table of FIG. 2), that is, when all of the
throttle-position sensor circuits of the TPS sensor system are
operating normally, the ECU 19 uses a throttle-opening indicative
first-sensor signal value TPO1 from the main throttle position
sensor (the first throttle position sensor 14A). When the central
processing unit (CPU) of the ECU 19 decides on the basis of the
diagnosis results (APS1NG=0, APS2NG=0, APSXNG=0, TPS1NG=0,
TPS2NG=0, TPSXNG=0) that the APS sensor system and the TPS sensor
system are both operating normally, the ECU 19 simultaneously
decides that there is no necessity for setting of a so-called
"limp-home" mode. Thus, a single APS sensor failure mode limp-home
enabling flag and a single TPS sensor failure mode limp-home
enabling flag are both reset to "0". At the same time, a
power-transistor OFF flag and a relay OFF flag are both reset to
"0". In such a case that the duplex APS sensor system and the
duplex TPS sensor system are both operating normally, an output
voltage signal at a second OR gate circuit 32 becomes a low level
and an output voltage signal at a third OR gate circuit 33 becomes
a low level, with the result that a power transistor and a relay,
which is used to drive or operate the throttle actuator 11, are
both turned ON. In this case, the throttle actuator 11 is driven,
so that the opening of the electronically-controlled throttle valve
9 is adjusted or controlled toward a desired throttle opening that
is set or determined on the basis of the "LOWER" selection value of
the two APS sensor values. At this time, the flags APS1NG, APS2NG,
APSXNG, TPS1NG, TPS2NG, and TPSXNG are all reset, and thus an
output voltage signal at a first OR gate circuit 31 is also
maintained at a low level. As a result, a warning lamp, which is
used for indication of a sensor failure, does not come ON.
In case that only the signal-mismatching indicative flag (APSXCA
and/or TPSXCA) in at least one of the duplex APS sensor system and
the duplex TPS sensor system is set at "1" (see the second line
from the top on each of the left-hand APS sensor system diagnosis
table and the right-hand TPS sensor system diagnosis table shown in
FIG. 2), the ECU 19 determines that the signal values from both of
the accelerator position sensors 1A and 1B are not reliable and/or
the signal values from both the throttle position sensors 14A and
14B are not reliable. In this case, the power-transistor OFF flag
and the relay OFF flag are both set at "1", the output voltage
signal at the first OR gate circuit 31 becomes a high level. As a
result, the warning light comes ON. The outputs from the second and
third OR gate circuits 32 and 33 become high levels, with the
result that the power transistor and the relay, serving to drive
the throttle actuator 11, are both turned OFF, thus de-energizing
the throttle actuator. As a consequence, a F/B selection value,
which is used for feedback control for the opening of the
electronically-controlled throttle valve 9, is first (temporarily)
set at a higher one (HIGHER) of the sensor signals from the two
throttle position sensors 14A (TPS1) and 14B (TPS2) by way of a
so-called select-HIGH process, and thereafter the throttle valve 9
is controlled toward the "default" opening and then maintained at
the "default" opening. The vehicle can run, therefore, at the
minimum necessary speed such as 40 Km/h. As may be appreciated, if
there is a "1" or a high-level input voltage signal at either input
terminal of the first OR gate circuit 31, the OR gate circuit 31
outputs a high-level voltage signal, so as to illuminate the
warning lamp.
In case that either one of the first and second
acceleration-position sensor failure decision flags APS1NG and
APS2NG is set at "1", that is, when the sensor failure of either
one of the accelerator-position sensors 1A and 1B is detected (see
the third to sixth lines from the top on the left-hand side APS
sensor system diagnosis table of FIG. 2), a single APS sensor
failure mode limp-home enabling flag is set at "1", the
power-transistor OFF flag and the relay OFF flag are both reset to
"0". In case of such a single APS sensor failure, as can be seen
from the rightmost column indicating the APS selection value, in
setting or estimating the throttle opening of the throttle valve 9,
the ECU 19 uses or selects the sensor signal value (APO1 or APO2)
of the unfailed APS sensor. For example, in presence of the second
APS sensor failure, that is, in case of APS1NG=0 and APS2NG=1 (see
the third and fourth lines from the top on the left-hand side APS
sensor system diagnosis table of FIG. 2), the accelerator-opening
indicative signal value APO1 of the first APS sensor is selected as
the APO selection value. Conversely, in presence of the first APS
sensor failure, that is, in case of APS1NG=1 and APS2NG=0 (see the
fifth and sixth lines from the top on the left-hand side APS sensor
system diagnosis table of FIG. 2), the accelerator-opening
indicative signal value APO2 of the second APS sensor is selected
as the APO selection value. Likewise, in case that either one of
the first and second throttle-position sensor failure decision
flags TPS1NG and TPS2NG is set at "1", that is, when the sensor
failure of either one of the throttle position sensors 14A and 14B
is detected (see the third to sixth lines from the top on the
right-hand side TPS sensor system diagnosis table of FIG. 2), a
single TPS sensor failure mode limp-home enabling flag is set at
"1", the power-transistor OFF flag and the relay OFF flag are both
reset to "0". In case of such a single TPS sensor failure, as can
be seen from the rightmost column indicating the TPS selection
value, in setting or estimating the throttle opening of the
throttle valve 9, the ECU 19 uses or selects the sensor signal
value (TPO1 or TPO2) of the unfailed TPS sensor. For example, in
presence of the second TPS sensor failure, that is, in case of
TPS1NG=0 and TPS2NG=1 (see the third and fourth lines from the top
on the right-hand side TPS sensor system diagnosis table of FIG.
2), the throttle-opening indicative signal value TPO1 of the first
TPS sensor is selected as the F/B selection value. Conversely, in
presence of the first TPS sensor failure, that is, in case of
TPS1NG=1 and TPS2NG=0 (see the fifth and sixth lines from the top
on the right-hand side TPS sensor system diagnosis table of FIG.
2), the throttle-opening indicative signal value TPO2 of the second
TPS sensor is selected as the F/B selection value. As discussed
above, in case that a single sensor failure occurs in either one of
the APS sensor system (1A, 1B) and the TPS sensor system (14A,
14B), and also in case that a single sensor failure occurs in each
of the APS sensor system and the TPS sensor system, usually
(without any decelerating condition of the vehicle), the throttle
actuator 11 is driven so that the opening of the
electronically-controlled throttle valve 9 is adjusted or
controlled toward a desired throttle opening based on the APO
selection value (the sensor signal value of the unfailed APS
sensor). The selection of the sensor signal value of the unfailed
sensor is effective to prevent the opening of the throttle valve 9
from being forcibly maintained at the "default" opening, thus
avoiding the vehicle speed from being limited to a low speed such
as 40 Km/h. In other words, by the use of the sensor signal value
of the unfailed sensor, the vehicle can run at a desired speed even
in the case of the single sensor failure in either one of the APS
and TPS sensor systems or in both of the APS and TPS sensor
systems. However, in the case of the previously-noted single sensor
failure (the single APS sensor failure and/or the single TPS sensor
failure), and additionally when a decelerating operation is made
according to the driver's wishes, for example, when the accelerator
pedal is released and thus the idle switch 17 is switched ON,
and/or when the brakes are applied and thus the brake switch 18 is
switched ON, an output voltage signal at a fourth OR gate circuit
34 becomes a high level. Owing to the presence of the single sensor
failure in at least one of the APS and TPS sensor systems, at least
one of the single APS sensor failure mode limp-home enabling flag
and the single TPS sensor failure mode limp-home enabling flag is
set at "1". Thus, an output voltage signal at a fifth OR gate
circuit 35 becomes a high level. Since the outputs of the fourth
and fifth OR gate circuits 34 and 35 are both high or 1, an output
voltage signal at a first AND gate circuit 36 becomes high or 1. As
a result, the second OR gate circuit 32 becomes high or 1, and
therefore the throttle-actuator driving power transistor is turned
OFF to de-energize the throttle actuator 11, thus holding the
throttle valve 9 at the "default" opening. In other words, with the
single APS sensor failure mode limp-home enabling flag set and/or
the single TPS sensor failure mode limp-home enabling flag set, the
ECU 19 performs the limp-home mode or the limp-in mode which allows
the engine/vehicle to be run/driven but with greatly reduced
performance (for example, a fixed limp-in speed of approximately 40
Km/h).
In case of the double sensor failure in the APS sensor system (1A,
1B), that is, when the two APS sensors are both failed (the
presence of shorted/opened signals from both the first and second
APS sensors 1A and 1B), or in case of the double sensor failure in
the TPS sensor system (14A, 14B), that is, when the two TPS sensors
are both failed (the presence of shorted/opened signals from both
the first and second TPS sensors 14A and 14B), the ECU 19
determines that the signal values from both the accelerator
position sensors 1A and 1B are not reliable and/or the signal
values from both the throttle position sensors 14A and 14B are not
reliable. Thus, the ECU 19 temporarily sets the APO selection value
at a "0" signal value in the presence of the double sensor failure
in the APS sensor system, and thereafter sets both of the
power-transistor OFF flag and the relay OFF flag at "1", to
de-energize the throttle actuator 11 and then to hold the throttle
9 at the "default" opening. In the presence of the double sensor
failure in the TPS sensor system, the ECU 19 temporarily set the
F/B selection value at a full-throttle opening, and thereafter sets
both of the power-transistor OFF flag and the relay OFF flag at
"1", to de-energize the throttle actuator 11 and to smoothly
quickly feedback-control the throttle valve 9 in a direction
decreasing the throttle opening, so that the throttle opening is
adjusted to the "default" opening. In this manner, the opening of
the electronically-controlled throttle valve 9 is held at the
"default" opening.
Hereunder described in detail is the fail-safe control procedures
performed when the unfailed APS sensor of the duplex APS sensor
system changes from normal to abnormal under a particular condition
where only one of the two APS sensors 1A and 1B is failed or when
the unfailed TPS sensor of the duplex TPS sensor system changes
from normal to abnormal under a particular condition where only one
of the two TPS sensors 14A and 14B is failed. Note that the term
"abnormal" means remarkable mismatching between a sensor signal
value from the unfailed APS sensor (the unfailed TPS sensor) and a
predetermined sensor-abnormality diagnostic criterion range or a
predetermined threshold (a predetermined sensor-abnormality
diagnostic criterion). The predetermined sensor-abnormality
diagnostic criterion range or the predetermined threshold is
preprogrammed under a specified condition, for example during a
decelerating condition of the vehicle or during idling. The term
"abnormal" never means a shorted/opened signal. The fail-safe
control related to the duplex TPS sensor system (14A, 14B) is
hereinafter described in detail.
In case that the decelerating operation is made by the driver at
the single TPS sensor failure mode where one of the two throttle
position sensors 14A and 14B is failed and thus the
throttle-opening feedback control for the electronically-controlled
throttle valve 9 is executed on the basis of the sensor signal from
the other throttle position sensor (the unfailed throttle-position
sensor), the idle switch 17 becomes energized (ON) with the
accelerator pedal released and/or the brake switch 18 becomes
energized (ON) with depression of the brake pedal. In such a
decelerating condition of the vehicle, the power transistor is
turned OFF, to switch the throttle actuator 11 from an operative
state to an in-operative state. With the throttle actuator 11 in
the in-operative, during the vehicle deceleration, the throttle
valve 9 is usually controlled toward its "default" opening, and
then held at the "default" opening. Under such a specified
condition that the throttle valve 9 is maintained at the "default"
opening during the engine/vehicle deceleration at the single TPS
sensor failure mode, a sensor signal value from the unfailed TPS
sensor is compared with a predetermined sensor-abnormality
diagnostic criterion range, namely an upper limit (a "default"
opening plus .alpha.) and a lower limit (a "default" opening minus
.alpha.) by means of a window comparator 37 whose output is
determined by way of a window function. The upper limit of the
predetermined sensor-abnormality diagnostic criterion range is
obtained by adding a predetermined margin .alpha. to the "default"
opening, whereas the lower limit of the predetermined
sensor-abnormality diagnostic criterion range is obtained by
subtracting a predetermined margin from the "default" opening. When
the sensor signal value from the unfailed TPS sensor is not within
the sensor-abnormality diagnostic criterion range, that is, when
the unfailed TPS sensor signal value is above the "default" opening
plus .alpha. or when the unfailed TPS sensor signal value is below
the "default" opening minus .alpha., the ECU 19 determines that the
unfailed TPS sensor is operating abnormally, and thus the relay for
the throttle actuator 11 is turned OFF. The window comparator 37 is
designed, so that its output voltage signal becomes high (or 1)
when the condition defined by a predetermined inequality (the
sensor signal value from the unfailed TPS sensor>the "default"
opening plus a ) is satisfied or when the condition defined by a
predetermined inequality (the sensor signal value from the unfailed
TPS sensor<the "default" opening minus .alpha.) is satisfied.
For the purpose of fail-safe in presence of transition of the
unfailed TPS sensor from normal to abnormal at the single TPS
sensor failure mode, a second AND gate circuit 38 is provided in
such a way that its input terminals receive the output signal from
the window comparator 37, the input data from the single TPS sensor
failure mode limp-home enabling flag terminal, and the output
signal from the fourth OR gate circuit 34, and its output signal is
fed into the third OR gate circuit 33. With the previously-noted
arrangement for the failsafe purpose in the duplex TPS sensor
system, when the state of the unfailed TPS sensor changes from
normal to abnormal during the vehicle deceleration at the single
TPS sensor failure mode, the second AND gate circuit 38 receives
high-level voltage signals from all of the window comparator 37,
the single TPS sensor failure mode limp-home enabling flag line,
and the fourth OR gate circuit 34. Under these conditions, the
output voltage signal at the second AND gate circuit 38 becomes
high (or 1), and thus the output voltage signal at the third OR
gate circuit 33 becomes high (or 1). As a result, the
throttle-actuator relay is turned OFF. In this manner, if the ECU
19 once determines that the unfailed TPS sensor is operating
abnormally in the single TPS sensor failure mode, the
throttle-actuator relay remains kept OFF. Even if the accelerator
pedal is depressed by the driver after the decision of abnormality
in the unfailed TPS sensor during the single TPS sensor failure
mode, the throttle actuator 11 is de-energized unconditionally and
thus the opening of throttle valve 9 is maintained at its "default"
opening, so that the ECU 19 performs the limp-home mode which
allows the engine/vehicle to be run/driven but with greatly reduced
performance (for example, a fixed limp-in speed of approximately 40
Km/h). As discussed above, the fail-safe control apparatus of the
embodiment can enhance a reliability of fail-safe control in the
duplex throttle-position sensor system.
The fail-safe control related to the duplex APS sensor system (1A,
1B) is as follows.
In case that the idle switch 17 becomes energized (ON) with the
accelerator pedal released at the single APS sensor failure mode
where one of the two accelerator position sensors 1A and 1B is
failed and thus a desired opening of the electronically-controlled
throttle valve 9 is set or determined on the basis of the sensor
signal from the other accelerator position sensor (the unfailed
accelerator position sensor), a sensor signal value from the
unfailed APS sensor is compared with a predetermined or
preprogrammed threshold value (simply a set value) correlating with
a usual accelerator pedal opening given during idling of the
engine, by means of a comparator 39. Actually, if the sensor signal
value from the unfailed APS sensor is above the predetermined
threshold value, then the output voltage signal from the comparator
would be a high output signal level (or 1). At this time, the ECU
19 determines that the unfailed APS sensor is operating abnormally,
and thus the throttle-actuator relay is turned OFF. For the purpose
of fail-safe in presence of transition of the unfailed APS sensor
from normal to abnormal at the single APS sensor failure mode, a
third AND gate circuit 40 is provided in such a way that its input
terminals receive the output signal from the comparator 39, the
input data from the single APS sensor failure mode limp-home
enabling flag terminal, and the output signal from the idle switch
17, and its output signal is fed into the third OR gate circuit 33.
With the previously-noted arrangement for the failsafe purpose in
the duplex APS sensor system, when the state of the unfailed APS
sensor changes from normal to abnormal during the idling period at
the single APS sensor failure mode, the third AND gate circuit 40
receives high-level voltage signals from all of the comparator 39,
the idle switch 17, and the single APS sensor failure mode
limp-home enabling flag line. Under these conditions, the output
voltage signal at the third AND gate circuit 40 becomes high (or
1), and thus the output voltage signal at the third OR gate circuit
33 also becomes high (or 1). As a result, the throttle-actuator
relay is turned OFF. In this manner, if the ECU 19 once determines
that the unfailed APS sensor is operating abnormally in the single
APS sensor failure mode, the throttle-actuator relay remains kept
OFF. As appreciated from the above, after the decision of
abnormality in the unfailed APS sensor during the single APS sensor
failure mode, the throttle actuator 11 is de-energized
unconditionally and thus the opening of throttle valve 9 is
maintained at its "default" opening, so that the ECU 19 performs
the limp-home mode which allows the engine/vehicle to be run/driven
but with greatly reduced performance (for example, a fixed limp-in
speed of approximately 40 Km/h). The fail-safe control apparatus of
the embodiment can also enhance a reliability of fail-safe control
in the duplex accelerator-position sensor system.
The entire contents of Japanese Patent Application No. P10-244114
(filed Aug. 28, 1998) is incorporated herein by reference.
While the foregoing is a description of the preferred embodiments
carried out the invention, it will be understood that the invention
is not limited to the particular embodiments shown and described
herein, but that various changes and modifications may be made
without departing from the scope or spirit of this invention as
defined by the following claims.
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